The invention relates primarily to a metal suspension half-cell for an accumulator at least comprising a housing for enclosing an electrolyte-containing suspension, an electrode in contact with the suspension and a membrane which can form a partition with a second half-cell which it is desired to cause to interact with the metal suspension half-cell in order to form an accumulator, the suspension also comprising additive particles in addition to metal particles of a selected metal and electrolyte.
A metal suspension half-cell of this type is disclosed in Netherlands Laid-Open Patent Application 75 08697.
The said publication describes a metal suspension half-cell in which a metal suspension, for example containing zinc, is incorporated and the structure of the metal constituent in the suspension corresponds to the maximum geometrical stacking of the grains or approaches this, while the amount of electrolyte in the suspension is essentially equal to the amount necessary to fill the spaces between the metal particles and to obtain ion transfer.
The suspension thus described in this publication has more the character of a paste and therefore has a relatively high viscosity.
In the half-cell which is described in this publication the viscous paste is allowed to circulate through the half-cell using a transporting electrode, such as a screw.
In order to lower the power for driving the screw, additive particles in the form of a lubricant are also added to the paste to facilitate pumping through the half-cell; the lubricant can be in the form of polytetrafluoroethylene or graphite. With regard to the addition, it is stated that this has no influence on the ion exchange.
The stability of the suspension is ensured by the virtually dense stacking of the metal particles, so that settling thereof is prevented.
As a result of the presence of a relatively small amount of fluid electrolyte in relation to the amount of material in particle form, saturation of the electrolyte with zincate will occur relatively rapidly in the case of a zinc suspension accumulator containing a basic electrolyte. As a result of such saturation, the current-supplying capacity of the accumulator will decrease relatively rapidly over time.
The aim of the present invention is to provide a metal suspension half-cell of the type described with which, on the one hand, a good stability of the suspension is guaranteed and, on the other hand, a larger amount of electrolyte can be present so that a greater amount of material formed during discharge of the half-cell can be dissolved.
A further aim of the invention is to provide a half-cell of the type described in which circulation of the suspension is no longer necessary.